My invention relates to a photographic printer and more particularly to a photographic printer which responds to electrical signals encoding information to be printed.
Various types of photographic duplicating machines are known in the prior art. For example, there is known an electrophotographic copier incorporating a photoconductor on the surface of which a latent electrostatic is formed for subsequent development and possible transfer to a sheet of paper. These machines have the advantage of being fast in operation, of producing copies of good quality and of being relatively inexpensive for the result produced. It is desirable that the advantageous characteristics of these machines be employed in printing data which is encoded in the form of electrical signals. It would be particularly desirable if an apparatus could be designed which could function both as a traditional photocopier and also as a printer of electronic information.
Efforts have been made in the prior art to use printers with photosensitive surfaces to print electronically encoded information. A system embodying one such effort is disclosed in IBM Technical Disclosure Bulletin, Vol. 19, No. 7, December 1976. Light from a common light source is directed through a thin slit to a plurality of liquid crystal light beam modulators which are activated by electrical signals selectively to allow light to fall upon a plurality of respective small areas on the surface of a photoconductive drum to form a latent electrostatic image of the information represented by the electrical signals. One difficulty with this apparatus is its large size, which renders it unsuitable for use in a machine which is designed to operate both as a printer of electronic information and a conventional photocopier. More significantly the system requires a large light source, much of the light produced by which is not used. In addition the source generates excessive heat which results in a further waste of energy.